This invention relates to recovery and re-use of scrap polyurethane, and is especially concerned with the provision of a process and composition for decomposing and dissolving polyurethane foams and adhesives, and to procedure for re-use of the resulting solution containing urethane polymer depolymerization components, for producing fresh urethane polymer.
Polyurethane foams and adhesives are extensively employed in industry at the present time. Thus, urethane polymers are employed throughout industry for the preparation of rigid, semi-rigid or soft polyurethane foam. Urethane polymers are produced basically by the reaction of a polyisocyanate, particularly diisocyanates, with hydroxyl-rich compounds containing at least two hydroxyl groups per molecule, such as glycols, polyesters, polyethers, and the like, or amine-rich compounds such as aromatic and aliphatic diamines and polyamines.
Since many urethane polymer foams are cross-linked, when preparing urethane polymer foam parts using for example metallic molds, it is particularly difficult to remove excess urethane polymer from such molds after formation of foam parts and removal thereof from the molds. Parting agents are frequently used in some industries for this purpose, and certain treating agents have heretofore been employed which soften the polyurethane foam so that excess foam on the mold can be more easily removed by hand. Treating agents of this type previously employed include superheated steam, N-methyl pyrrolidone, chlorinated hydrocarbons, and the like. However, in most applications, in spite of the use of such softening agents, some hand removal of the excess foam is necessary.
Further, the polyurethane foam manfacturing industry is known to discard millions of pounds of scrap foam annually in this country, with additional similarly substantial quantities being discarded world-wide, that is outside the United States. The chemicals contained in such scrap are lost, and no commercially successful recovery process for such chemicals has heretofore been devised.
Various procedures have been disclosed in the prior art in seeking to solve the problem of recovery of the chemicals in scrap urethane polymers. McElroy (U.S. Pat. No. 3,117,940) teaches that urethane polymers can be dissolved in amines such as diethylene triamine, or diamino toluene. However, the cost of the reagent makes this method prohibitively expensive, since approximately 0.3 pound of amine are consumed for each pound of foam, apart from excess amine which has to be used as solvent and which must be recovered by distillation. Matsudaira, et al. (U.S. Pat. No. 3,404,103) discloses addition of sodium hydroxide to the amine, to regenerate the amine solvents. This process theoretically consumes only sodium hydroxide, but in practice about 10% of the amine solvent is consumed. However, because of the high price of suitable amines, this process has also proved to be too costly in practice. U.S. Pat. No. 3,708,440 to Frulla, et al., teaches that scrap urethane foam can be dissolved in glycols in the presence of an alkanolamine, but the excessive periods of heating required have militated against the use of this process on a commercial scale.
It is an object of the present invention to provide procedure and compositions for readily decomposing polyurethane, and to prepare useful chemical mixtures or solutions from scrap polyurethane. Another object is to provide procedure for utilization of such chemical mixtures or solutions for preparing fresh polyurethane foams and resins.